1. Field of the Invention
The invention relates to a memory device and fabrication thereof, and in more particularly to a phase change memory device and a fabrication thereof.
2. Description of the Related Art
Phase change memory devices have many advantages, such as high speed, lower power consumption, high capacity, greater endurance, better process integrity and lower cost. Thus, phase change memory devices can serve as independent or embedded memory devices with high integrity. Due to the described advantages, phase change memory devices can substitute for volatile memory devices, such as SRAM or DRAM, and non-volatile memory devices, such as Flash memory devices.
FIG. 1A shows a conventional T-shaped phase change memory device. Referring to FIG. 1A, a conventional T-shaped phase change memory device sequentially comprises a bottom electrode 102, a heating electrode 104, a phase change layer 106 and a top electrode 108 with the cylinder-shaped heating electrode 104 contacting the phase change layer 106. The dimensions of the contact region 110 between the heating electrode 104 and the phase change layer 106 is determined according to dimensions of the heating electrode 104, such that controlling the dimensions of the contact region 110 is difficult. In addition, fabrication of the heating electrode 104 of the T-shaped phase change memory device at least comprises forming an opening utilizing etching, filling the opening with conductive materials and chemical mechanical polishing the conductive materials. The process is relatively complicated, and quality of the heating electrode 104 formed thereby is inadequate.
FIG. 1B shows a cross section of another conventional phase change memory cell with a confined structure. In FIG. 1B, an opening between spacers 158 overlying a bottom electrode 152 and a heating electrode 154 is filled with phase change layer 156 to form a via 160. The phase change layer 156 connects the heating electrode 154 through the via 160. Via 160, however, must be formed as an arc-shaped using a spacer process, such that phase change layer 156 can be more easily filled into the opening between the spacers 158 when via 160 is formed. Currently, plasma vapor deposition or evaporation is utilized to fill the opening with phase change materials when forming via 160. It is very difficult, however, to achieve via 160 without defects.